In the construction industry, it is often necessary to insert caissons into the earth. As examples, caissons are inserted into the earth during new construction as part of a foundation for a structure; caissons are also commonly driven under a bridge or the like when providing additional structural resistance to earthquake damage.
To insert a caisson into the earth, a large driving force must be applied thereto. Often, vibratory devices are employed to introduce a vibratory force along the axis of the caisson during the driving process. The combination of a static driving force with a dynamic vibratory force is usually sufficient to overcome the earth's resistance and allow the caisson to be inserted therein.
A clamping assembly must be provided to allow vibratory forces to be effectively transmitted to the caisson. Such clamping assemblies have heretofore normally been adapted to engage the upper end of the caisson. In this case, sufficient clearance must be present above the upper end of the caisson to accommodate the clamping assembly and vibratory device.
The Applicant is also aware of at least one instance where a hole was formed in a plate and vibratory devices mounted on the plate. The caisson was passed through the hole in the plate and hydraulic clamps attached to the plate engage the side walls of the caisson to fix it relative to the plate. While the clamp assembly engages the side walls and not the top end of the caisson, the clamp assembly and vibratory devices must be raised above the upper end of the caisson to pass the caisson through the hole in the plate. Accordingly, this arrangement still requires clearance above the caisson upper end to accommodate the clamping assembly and vibratory device.
In new construction, the construction process may be scheduled to ensure that adequate clearance is present above the caisson to allow the clamping assembly and vibratory device to be raised over the upper end thereof.
In other situations, such as when caissons are being inserted under a bridge or other previously erected structure, the available clearance may be limited. In such cases, the caisson must be shortened such that the total length of the caisson, clamping assembly, and vibratory device fits within the available clearance. Using a shorter caisson means that caisson sections must be welded together such that the entire caisson extends into the earth to the required depth. Welding caisson sections together is a time and labor intensive process that drives up the cost of inserting caissons into the earth.
Accordingly, the need exists for methods and apparatus for attaching a vibratory device to a caisson that can be used effectively in spaces with restrictive headroom.
From the following discussion, it will be apparent that this and other problems with prior art caisson clamping assemblies are solved by the present invention.